Punch and die



B. cHNEIDER r-:r A1. 2,111,156

PUNCH AND DIE March 15, 193&.

Filed July 18. 1936 7 i w1 I. 1-5% o al. j f a, /Wmm Y.. i l.: l. y? 4, //M\ A Patented Mar. l5, 1938 PUNcH PATEN'r OFI-ics AND DIE v Bruno schneider, kunnen, and oscar Msi-- f quard, St. Albans, N. Y.

" Application vJuly 1s.

4 Claims This invention relates to improvements in punches and dies commonly employed foripunohing discs of various shapes from materials ofA sheet form, but more particularly for use in cutting blanks of any desired shape from sheet mica.

for use as insulation in radio apparatus and the" like.

As is well known in the art, it has heretofore been extremely difficult to punch mica sheets and 1o at the same time prevent a slight separation of the strata along he sheared edges. We have found through e ustive experimentation and observation that this is caused by a very slight bending of the mica at the point where the edge of the punch passes the edge-'oi'l thedie, and

may be due either to' too great clearance, to improperl holding of the mica against the face of the punch, to an accumulation of mica dust that interferes with clean shearing, or to a combination of these causes.- Separation of the strata vmay easily occur in sheets of mica having Va. thickness of only .0015 in. vto .002 in.. andwhen mica blanks are thus injured and later-used as laminated insulation in radio "equipment, and particularly in condensers,imperfect results are practically sure to follow. To overcome these conditions we have deveiopedthe .punch and die apparatus illustrated in the accompanying drawing, in which:

Fig. 1 is a cross section'through the central plane of the mechanism;

Fig. 2 is a somewhat-enlarged view, in section, of the die and knock-out; l

Fig. 3 is a bottom Viewl of the knock-out.

IIn Fig. 1, yI representsthe base plate of the apparatus, which may beinstalled inl any press of suitable design by bolting tothe bedzof the press. 2 is a stripper plate for stripping the sheet away from the punch in theusual manner, 4o and is held in ,proper alignment with the base plate by means of screws, .2, which are1free to' slide in guide holes in the plate I. The screws 3 are held rigidly in stripperpla'te 2 by Ameans of lock nuts 4, against which thespring's '45 5 are compressed when the stripper plate is forced downward :by .the dow'nstroke of the ram of the press, which is not shown. vA punch base 6 is fastened to basepplate by means of `screws 1, and heldin proper alignment by dowels not shown.- By means of screws 8 the minch'l is fastened firmly to punch base 6.4 'Ihe foregoing parts comprise the stationary element of the apparatus, which in the illustration is the punch, vor male portion of the set. 4

directly above In the movable portion shown 1936, ser-isi No. 91,216

the punch assembly, the 'die plate- I0 is' securely fastened to die holder II by a. suitable number of screws I2, and held in alignment by means of dowels I3. In the design shown an auxiliary piercing punch I4 is provided to cut a hole' in the blank vvnue the blank is being punched; the scrap being discharged downward through hole I5 extending through punch 9, punch base 6 and base plate I. Piercing punch Il is securely held in punch plate I6 by a drive t in a hole drilled therein, and plate I6 is seated against the die base I1, which has a boss lil fitted into a recess in die holder I I. Boss I8 is preferably cylindrical in form vto simplify construction, and its upper surface is depressed somewhat inside an annular rim I8a to form a shallow open chamber I9. A knock-out, 2li, having acontour similar to punch 9, and being only slightly smaller than .punch 9, is equipped with two guide posts 2| whose lower ends are threaded, and screwed into correspondingly tapped hogles in knock-out 2li. These guide posts 2| are aligned in properly fitted holes provided therefor in punch platel I6, and 'are provided withdillister heads which slide in correspending holes in die base I1, the shoulders `formed by these heads serving to limit the down- `wardV travel of knock-out 20 by abutting against punch plate I6. Guide posts 2| have longitudinal slots 2Ia extending throughout their-length, and .providing air passages connecting between the spaces surrlounding Isprings 22` and the space between' knock-out 20 and die plate Ill; and also into the recessed portion of knock-out Knock-out 20 is normally held down by pressure of .compression springs 22, which bear against guide posts 2i and react against bearing plate 22, which has a ole 24 in its center. Bearing plate 23 is held in contact with the annular rim Ila of die base I'I. by means of screw A25 threaded into die holder IIA, this screw having a central hole v26 throughout its length and being concentric-with bearing plate :a and its central,

hole 2l.

In thel upper part of die holder II is a cylinder 2'| in "which is fitted a'piston (2l having `a tail rod 22a guided .in cylinder head 29', which is fastened to die holder I in-any convenient manner, as by screws 30. an serves to limit theupward travel of piston 2l. A compression spring 3l is held at itsupper end in a hole ila in the piston Il, and at its lower end in a similar hole SIb in the die holder Il, where it bears against stud 2l.

n t the top of its lstroke. One or more ports of the sitting Il tends 150 hold the out 20. The purpose of this will be hereinafter` explained.

In Fig. 2 is shown a somewhat enlarged view of knock-out 20 with a portion of the surrounding mechanism. One diflicultyin punching mica heretofore has been due to an accumulation of mica dust, -in greater or less amounts, on the work itself, tending to prevent close contact between the knock-out and the faceof the punch. To counteract this tendency we relievev the face of the knock-out 20 by milling out its entire face, or underside, as shown ln the section, Fig. 2, and in the bottom view, Fig. 3, leaving only a nar-V row rim around the periphery ofthe knock-out -to bear against the mica sheet. This provides a space in which mica dust can enter without being firmly squeezed between the knock-out and the work, and it also greatly reduces the contact surfacey of knockeout -20 and correspondL ingly increases its unit pressure against the work, thusinsuring smooth` cutting by the shearing action of the punch 9 acting in die I0. To prevent an accumulation of mica dust in the space between the knock-out 2l) and die plate I9, we

provide a strong current of air acting outwardly from the space intervening between these two parts. When the die assembly is forced downward by a down stroke of the press ram (not shown), the studs .34 iirst come into contact with stripper 2, forcing it downward and slightly below the iiush surface of punch 9, and permitting the mica sheet to come in contact therewith. Next, knock-out 20 strikes the sheet and holds it rmly against the face of the punch 9. As the die assembly continues to descend, guide posts 2l vremain stationary, and bearing plate 23, held in xed relationship to the die assembly, compressesthe springs 22, thus increasing the pressure of the knock-out, 20, against the work through the reaction of punch 9. As the die assembly approaches the lower limit of the down stroke, the blank is sheared, and after the press passes the .dead center the reverse of these operations takes place. But, as the die assembly continues to rise, tail rod 28A of piston 28 strikes a cross bar 33 which is bolted to the press frame (not shown), and the air contained in cylinder 21 is suddenly compressed by the upward movement of cylinder 21 in relation tothe piston 28, which is now stationary. The air thus compressed in cylinder 2 1 is forced downward, through -holes 3 lb, 26, and 24, through recess I9, around. and through springs '22 and the air passages 2Ia in guide posts 2| into the space between die plate I9 and knock-out 20. Its means '-of escapeis partly through the narrow peripheral space at the lower'edg'e of the die, through whichj it rushes under considerable velocity, carrying with it any dust which would otherwise tend to be caught in this space, and

where experience has shown it will invariably collect in die sets-of the ordinary type; and partly through the air passages 21;.; in 'knock-out'29,

and into the'recessed portion of knock-out 20, where its action notl only forces the punched blank away from the knock-out and prevents it from adhering thereto, but also expels -any dust that might otherwise accumulate on knockout 20. On the down stroke ofthe press, air is again admitted to cylinder 21 through a suitable number of ports 32, when piston 28 has been released by bar 33 and is forced upward by spring-3l.

conceivably, the same results might beac-i complished by using a small bellows actuated by the reciprocating movements of the press ram, or by leading compressed air from an external source through a flexible connection into the space surrounding knock-out 20, and causing it to act intermittently by opening and closing a valve through the reciprocal movement of the die assembly. But experiments show that this latter practice produces poor results, owing to the accumulation of moisture in air thus compressed and stored. We therefore prefer to use the method set forth above, in which the air compressor is built integral with the die set.

As a further improvement in our invention,

we provide means for preventing the -sheared the lower ends of studs 34 are slightly below the.

plane of the working face of knock-out 20. Thus, during` the down stroke of f the die assembly, stripper plate 2 is depressed belowthe cutting edges of punch 9 before knock-out 20 strikes the work. After knock-out 20 has seized and held the sheet against punch 9, die plate I9 continues downward until its cutting` edges have passed the cutting edges of punch 9, thus shearing the material. pressed, and knock-out 20 retreats-slightly into the recess in die I9, the work necessarily following it. Piercing punch I4 also enters the hole in punch 9, cutting a hole in the blank. After the ram of the press passes the dead center and pressure of springs 5, disengaging the scrap from punch 9. This sequence of operations prevents the punched blank from being pressed again into or through the hole already cui| in the sheet or scrap, thus insuring better results, as such repressing into the hole already cut would tend to injure the edges of the blank and separate the strata.v I

While we have described our invention with great particularity with regard to a specific embodiment thereof, it is not to beconstrued that we are limited in scope to the identical design as shown in the drawing and described herein, for modifications of detail and a different arrangement of the parts could be made by those skilled in the art without departing from the spirit of our invention as covered in the following claims.

whatwe claim is:

1. A punch and die set for punching blanks from sheet material, including in combination a source of supply of air unde'r pressure, means for keeping the blanks separated from the scrap after punching, means reciprocating within the die for clamping the work against the face of Simultaneously springs 22 are com-v the punch, one or morexair passages communicating from the source of supply of compressed air to the internal opening in the die, and one or more air passages communicating from the source of supply of compressed air to the working face of said clamping means.

2. A punch and die set for' punching blanks from sheet material, including in combination an air compressor integral with the moving element of the set, means reciprocating Within the die for clamping the Work against the face of the punch, and one or more air passages communicating from the air compressor cylinder to the internal opening in the die and between the die and the said clamping' means.

3. The combination, in a punch and die set for punching blanks from sheet stock of an air compressing cylinder, means for clamping the stock against the face of the punch prior to the punching of the stock, air passages communieating between the air compressing cylinder and an enclosed space surrounding the said clamping means, means to strip the scrap from the punch following the punching of a blank, and means co-actingwith the clamping means and the scrap stripping means to prevent the blank from re-entering the hole left in the scrap, and throughout the operation to maintain the sheet stock substantially in the form of a plane surface.

4. In a punch and die set incorporating a stationary punch and movable die, the combination of means for compressing air, means for clamping the stock against the face of the punch during a predetermined portion of the cycle of motion of the die, said clamping means having its working ysurface confined to a narrow raised rim contiguous to the cutting edges of the punch and die, and a plate arranged to strip the scrap from the punch, the said plate having adjustable means for controlling its action in relation to the release of a punched blank by the movement of the said clamping means away from the punch.

BRUNO SCHNEIDER. OSCAR MARQUARD. 

